This invention relates to a self-propelled harvesting machine and more particularly to an improved frame for the traction unit of a self-propelled windrower or the like.
A self-propelled windrower conventionally includes a rearward traction unit that carries a forward, transversely elongated harvesting platform, the traction unit having a pair of forward drive wheels and one or more rearward caster wheels, the machine being steered by controlling the relative speeds of the front drive wheels. While originally such machines utilized only a single rear caster wheel and had a generally triangular shape, with the front wheels being driven through belt drives, more recently, especially in the larger, heavier duty machines, the traction unit frames have featured hydrostatically driven front wheels, with a pair of rearward caster wheels in fore and aft alignment with the front drive wheels, the rear caster wheels being mounted on an axle structure that oscillated about a fore and aft axis. An early machine of the above general type is shown in U.S. Pat. Nos. 3,459,273, and 3,474,607, both of which are assigned to the assignee herein. The machine shown in said patent included a generally rectangular frame with generally fore and aft opposite side frame members and a transverse front beam attached to the forward ends of the opposite side frame members and extending laterally outwardly of the side frame members, a pair of wheel support housings extending downwardly from the opposite ends of the front frame member with the wheel housings being spaced outwardly of the side frame members.
In such machine, the header support linkages have conventionally been attached to the wheel support housings. Such machines are operated on relatively rough terrain with the header normally riding on the ground, the forces due to the weight of the header and the engagement of the header with ground irregularities or foreign objects being transmitted to the windrower through the drive wheel support housings.
A later version of a frame for a self-propelled forage harvester traction unit is shown in U.S. Pat. No. 3,897,840. The frame in said machine also features a main transverse front beam with the wheel support housings attached to and extending downwardly from the opposite ends of the front beam and a pair of side frame members having their forward ends connected to the front beam inwardly of the wheel support housings and tapering rearwardly to a rear transverse frame member. To strengthen the connection of the wheel support housings to the generally horizontal subframe of the traction unit, a second transverse beam is provided rearwardly of the first, the second transverse frame member also being welded to the side frame members as well as to the wheel support housings.